On the status of Megatherium (Pseudomegatherium) tarijense (Xenarthra: Megatheriidae)

GERARDO, DE IULIIS; FRANÇOIS, PUJOS; GIUSEPPE, TITO

Paris, Francia

Congreso; 8th International Congress of Vertebrate Morphology; 2007

Society of Vertebrate Morphology

    Knowledge of the history and anatomy of megatheriine ground sloths has been based largely on material recovered from Brazil and Argentina. In recent years, however, much new material described from northwestern South America has altered our ideas of the evolution of this clade and has resulted both in the recognition of several new taxa and the validation of species named on sparse remains. Falling in the latter group is Megatherium (Pseudomegatherium) tarijense Gervais and Ameghino, 1880, which is based on a complete but eroded calcaneum from the Pleistocene of southern Bolivia. Most authors of the past century viewed this species as poorly defined and probably a synonym of Megatherium (Megatherium) americanum. Confusion over the status of M. (P.) tarijense was also caused in large part by the presence of M. (M.) americanum in the Bolivian Pleistocene. However, well preserved and nearly complete remains of several individuals suggest that M. (P.) tarijense is indeed valid. These remains include abundant remains from the Tarija Basin (Bolivia) housed in the Field Museum of Natural History (USA) and the Museo Nacional de Paleontología y Arqueología de Tarija (Bolivia); and from Yantac in the Peruvian Andes housed in Universidad Nacional de Ingeniería (Peru). M. (P.) tarijense differs from M. (M.) americanum mainly in its smaller size, shallower mandibular ramus, reduced size of the humeral deltopectoral crest, and less twisted femur.